(a) Field of the Invention
The present invention relates to an automatic transmission for a vehicle, and more particularly, to a planetary gear train of an automatic transmission for a vehicle that realizes, by minimal complexity, at least ten forward speeds, thereby improving power delivery performance and fuel consumption due to multi-stages, and improving driving stability of a vehicle by utilizing a low rotation speed of an engine.
(b) Description of the Related Art
Generally, in the automatic transmission field, achieving more shift stages is a technology for maximizing fuel consumption and driving efficiency and has been researched, and recent increases in oil prices are triggering competition in enhancing fuel consumption of a vehicle. In particular, research on an engine has been conducted to achieve weight reduction and to enhance fuel consumption by downsizing, and research on an automatic transmission has been performed to simultaneously provide improved drivability and fuel consumption by achieving more shift stages.
In particular, to achieve more shift stages for an automatic transmission, the number of parts, particularly the number of planetary gear sets is typically increased and installability, production cost, weight, and/or power flow efficiency based on total length of transmission increases. Therefore, to maximally enhance fuel consumption of an automatic transmission having more shift stages, it is important for better efficiency to be derived by a smaller number of parts.
Accordingly, an eight-speed automatic transmission has recently been introduced, and a planetary gear train for an automatic transmission enabling more shift stages is continuously required. However, the majority of general automatic transmissions having more than eight speeds include three to four planetary gear sets and five to six control elements (friction element), in this case, total length is increased, which has drawbacks of deteriorating installability. As a result, plural rows structure in which planetary gear sets are on planetary gear sets has been adopted, or a dog clutch has been applied in place of wet control elements. However, in this case, applicable structure is restricted and shift feel is deteriorated by applying the dog clutch.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.